DROP FUNCTION udf_name
DROP FUNCTION
statement deinstalls a `user-defined function UDF with the given name. On success, the function is no longer available for use in subsequent queries. Pending concurrent queries will not be affected and the library unload, if necessary, will be postponed until those queries complete. Example:
> DROP FUNCTION avgmva;
mysqlQuery OK, 0 rows affected (0.00 sec)